AQUATIC TOXICITY OF ONE DIMENSIONAL CARBON - MOspace

142 Pages·2010·5.75 MB·English

AQUATIC TOXICITY OF ONE DIMENSIONAL
CARBON NANOMATERIALS

A dissertation presented to
The Faculty of the Graduate School
at the University of Missouri-Columbia

In Partial Fulfillment
of the Requirements for the Degree of

Doctor of Philosophy

by
JOSEPH NGANGA MWANGI

Dr. Baolin Deng, Dissertation Supervisor
July 2010
The undersigned, appointed by the Dean of the Graduate School, have examined the dissertation
entitled

AQUATIC TOXICITY OF ONE DIMENSIONAL CARBON NANOMATERIALS

Presented by JOSEPH NGANGA MWANGI
a candidate for the degree of
Doctor of Philosophy,
and hereby certify that, in their opinion, it is worthy of acceptance

____________________________________________
Dr. Baolin Deng, Civil and Environmental Engineering

____________________________________________
Dr. Tom Clevenger, Civil and Environmental Engineering

____________________________________________
Dr. Kathlein Trauth, Civil and Environmental Engineering

____________________________________________
Dr. Hao Li, Mechanical and Aerospace Engineering

____________________________________________
Dr. Chris Ingersoll, United Sates Geological Survey
Ni wega muno
Esther Wanjiku,
Naomi Murugi,
Faith Wakanyi,
Mary Mugure,
Newton Mwangi.

Thanks to my relatives and friends for support during the study.
ACKNOWLEDGEMENTS
I would like to thank Dr. Baolin Deng for guidance during the entire study and my
dissertation committee members Christopher Ingersoll, Hao Li, Tom Clevenger and
Kathleen Trauth for their time and effort in reading the dissertation and offering valuable
suggestions to improve it. The use of laboratory resources at the United States Geological
Survey, Columbia Environmental Research Center, the knowledge and expertise from the
Toxicology Branch staff made the production of this dissertation possible and is
appreciated. I thank Tom Quinn, Jack Tanner, and Lesa Beamer at the Structural Biology
Core for use of the Dynamic Light Scattering instrument for material size analysis and
Lou Russ and Melainia McClain of the Electron Microscopy Core Facility for TEM and
SEM analyses at the University of Missouri (MU).
I thank the MU Graduate School for the Missouri Alliance for Graduate
Education and Professoriate Fellowship and the United States Environmental Protection
Agency (EPA) for the research funds through the STAR program (Grant #RD 83331601-
0). Other contributions appreciated were from the US Department of Education (DOE)
Graduate Assistance to MU in Areas of National Need (GAANN).

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ABSTRACT
This research determined the toxicity of one dimensional carbon nanomaterials
(CNMs) to benthic invertebrates. The study hypothesized that one-dimensional CNMs in
water and sediment were toxic to aquatic organisms and that toxicity was due to metals
solubilized from CNMs upon contact with water or sediment, the CNMs with metals or
CNMs without metals, and that factors affecting toxicity include sonication, type and
sources of CNMs, and sediment characteristics. Tests were conducted with as-produced
or modified carbon nanotubes (CNTs) from commercial sources or silicon carbide
nanowires (SiCNW). There were three primary studies: (1) toxicity to aquatic
invertebrates of SiCNW in water or sediment exposures, (2) toxicity to aquatic
invertebrates of CNT in water exposures, and (3) toxicity to aquatic invertebrates of
Multi-walled CNT (MWCNT) in sediment exposures. The amphipod Hyalella azteca, the
midge Chironomus dilutus, the oligochaete Lumbriculus variegatus and mussels
Lampsilis siliquoidea or Villosa iris were selected as representative test organisms
because they are typically used in toxicity testing of contaminants in water and sediment.
In the SiCNW study, acute 48-h exposures to sonicated and non-sonicated SiCNW were
conducted with amphipods and 96-h exposures to sonicated SiCNW were conducted with
midge, oligochaetes and juvenile mussels. In addition, 10-d exposures of amphipods to
sonicated SiCNW layered on a sediment surface or mixed with sediment with the daily
replacement of the overlying water were performed. In the CNT water study, short-term
14-d water-only tests were conducted by exposing amphipods, midge, oligochaetes, or
mussels to a thin layer of CNTs with the periodic replacement of water.
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In the MWCNT sediment study, 14- and 28-d whole-sediment toxicity tests were
conducted by exposing amphipods to MWCNTs spiked into eight reference sediments
(99:1 sediment to MWCNTs on a dry weight basis) also with the periodic replacement of
the overlying water. The sediments evaluated in the MWCNTs spiking study had
different amounts of total organic carbon (TOC) and acid volatile sulfides (AVS), which
could affect the toxicity or distribution of MWCNTs in the sediment and could also affect
the potential toxicity associated with dissolved metals associated with the MWCNTs.
In the SiCNW study, sonicated SiCNW were toxic to the amphipods but not to the
midge, oligochaetes or mussels. The non-sonicated SiCNW were not toxic to amphipods
in acute water exposures. The survival of amphipods exposed to sonicated SiCNW
layered on the sediment surface or mixed in with the sediment was not significantly
different from amphipod survival in the control. However, the amphipods growth was
significantly reduced in both exposures to SiCNW, layered on the sediment surface and
mixed in with the sediment, relative to the growth in the control sediment without the
addition of SiCNW. In the CNT water-only study, the survival of the invertebrates was
significantly reduced in three as-produced CNTs but not in two modified CNT samples
(i.e., cleaned with nitric acid and washed with water or mixed with a metal complexing
agent) relative to the control. In most cases, the growth of the test organisms was also
significantly reduced with exposure to CNTs. During the exposures of the organisms to
the CNTs, they were coated with the CNTs and they also ingested and accumulated it in
their guts.

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In the CNT sediment-spiked study, the survival of the amphipods was typically
not reduced. However, the biomass of amphipods was significantly reduced in three out
of the eight sediments spiked with CNTs compared to the control sediment. The metal
concentrations in the overlying water also were only slightly elevated in the spiked
sediments relative to the concentrations in the control sediment. These results show that
while metals may be released from the MWCNTs, the binding capacity of the evaluated
sediments was likely sufficient to limit the bioavailability of the metals to the amphipods
during exposures. Specifically, MWCNTs spiked in sediments with less than
approximately 1% TOC or with a high percentage of sand were toxic to amphipods.
These results demonstrate that growth was a more sensitive endpoint than survival for the
amphipods. The 14-d whole sediment tests also indentified sensitive sediments where 1%
MWCNTs spiked in sediment reduced the growth of amphipods but not significantly
relative to amphipods exposed to control sediments. The 14-d tests again identified
growth as a more sensitive endpoint than survival of the amphipods exposed to CNTs in
sediments. The 28-d whole sediment exposures were conducted with selected sensitive
sediments. The 28-d tests are relevant in the assessment of the environmental impact of
the CNTs because they are hydrophobic and may accumulate in sediments with the
potential to adversely affect the growth of amphipods. In the 28-d whole sediment tests
with two sensitive sediments, amphipod growth was significantly reduced in exposures to
1% MWCNTs spiked in sediment relative to amphipods in control sediment and
demonstrated that growth was a more sensitive endpoint.

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Overall, the toxicity of the CNMs (CNTs or SiCNW) appears to be the effect of
the coating of respiratory surfaces or the blocking of the digestive tract of the exposed
benthic invertebrates. The CNTs appear to smother the organisms and may interfere with
their ability to feed. The metals dissolution from the as-produced CNTs could also have
contributed to the toxicity. The toxicity test results with the selected CNMs, test
organisms and the sediments do not disprove the study hypothesis.
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS……………………………………………………………….ii
ABSTRACT……………………………………………………………………………...iii
ACRONYMS…………………………………………………………………………….xv
Chapter
1. INTRODUCTION………………………………………………………………...1

Nanomaterials and nanotechnology………………………………………1
Carbon nanomaterials………………………………………………….....2
Toxicity of chemicals in biological organisms……………………………3
Cytotoxicity of carbon nanotubes…………….…………………………...4
Toxicity of carbon nanomaterials to aquatic organisms…………………..6
Research problem and study approach…………………………………..10

REFERENCES…………………………………………………………………..12
2. TOXICITY OF SILICON CARBIDE NANOWIRES
TO SEDIMENT-DWELLING INVERTEBRATES IN
WATER OR SEDIMENT EXPOSURES………………………………………..19

ABSTRACT……………………………………………………………………...19
INTRODUCTION……………………………………………………………….20
MATERIALS AND METHODS………………………………………………...22
Preparation of silicon carbide nanowires………………………………...22
Test organisms…………………………………………………………...23
Water-only toxicity tests…………………………………………………24
Sediment toxicity tests…………………………………………………...26
Data analysis……………………………………………………………..29

RESULTS AND DISCUSSION…………………………………………………29

Sample characterization………………………………………………….29
Water-only toxicity tests…………………………………………………34
Sediment toxicity tests…………………………………………………...39

REFERENCES…………………………………………………………………..42

SUPPORTING INFORMATION………………………………………………..47

3. TOXICITY OF CARBON NANOTUBES TO
FRESHWATER AQUATIC INVERTEBRATES ……………………………...48

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ABSTRACT……………………………………………………………………...48
INTRODUCTION……………………………………………………………….49
MATERIALS AND METHODS………………………………………………..52

Materials…………………………………………………………………52
Toxicity tests……………………………………………………………..52
Sample characterization and analysis……………………………………56
Data Analysis…………………………………………………………….57

RESULTS………………………………………………………………………..57

Characteristics of CNTs………………………………………………….57
Toxicity tests……………….…………………………………………….61
EDTA range finder tests…………………………………………………65
Soluble metals during toxicity tests……………………………………...65

DISCUSSION……………………………………………………………………66

REFERENCES…………………………………………………………………..72

SUPPORTING INFORMATION………………………………………………..76
4. TOXICITY OF MULTI-WALLED CARBON NANOTUBES
SPIKED IN WHOLE SEDIMENT TO AN AMPHIPOD
(HYALELLA AZTECA)………………………………………………………….83

ABSTRACT……………………………………………………………………..83
INTRODUCTION……………………………………………………………….85

MATERIALS AND METHODS………………………………………………..87

Testing materials………………………………………………………..87
Spiking sediment with CNT……………………………………….........88
Toxicity tests……………………………………………………………89
Distribution of CNT in sediment………………………………………..91
Statistical analysis………………………………………………………92

RESULTS………………………………………………………………………..92

Water quality…………………………………………………………….92
Toxicity of CNT-Spiked sediments………………………………...........93
14-d tests…………………………………………………………………93
28-d tests…………………………………………………………………95
Distribution of CNTs in sediment……………………………………….96

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